title: Granulocyte-macrophage colony stimulating factor (GM-CSF) enhances cumulus cell expansion in bovine oocytes.
abstract: BACKGROUND
  The objectives of the study were to characterize the expression of the α- and β-subunits of granulocyte-macrophage colony stimulating factor (GM-CSF) receptor in bovine cumulus cells and oocytes and to determine the effect of exogenous GM-CSF on cumulus cells expansion, oocyte maturation, IGF-2 transcript expression and subsequent competence for embryonic development.
  
  
  METHODS
  Cumulus-oocyte complexes (COC) were obtained by aspirating follicles 3- to 8-mm in diameter with an 18 G needle connected to a vacuum pump at -50 mmHg. Samples of cumulus cells and oocytes were used to detect GM- CSF receptor by immunofluorescence. A dose-response experiment was performed to estimate the effect of GM-CSF on cumulus cell expansion and nuclear/cytoplasmic maturation. Also, the effect of GM-CSF on IGF-2 expression was evaluated in oocytes and cumulus cells after in vitro maturation by Q-PCR. Finally, a batch of COC was randomly assigned to in vitro maturation media consisting of: 1) synthetic oviductal fluid (SOF, n = 212); 2) synthetic oviductal fluid supplemented with 100 ng/ml of GM-CSF (SOF + GM-CSF, n = 224) or 3) tissue culture medium (TCM 199, n = 216) and then subsequently in vitro fertilized and cultured for 9 days.
  
  
  RESULTS
  Immunoreactivity for both α and β GM-CSF receptors was localized in the cytoplasm of both cumulus cells and oocytes. Oocytes in vitro matured either with 10 or 100 ng/ml of GM-CSF presented a higher (P < 0.05) cumulus cells expansion than that of the control group (0 ng/ml of GM-CSF). GM-CSF did not affect the proportion of oocytes in metaphase II, cortical granules dispersion and IGF-2 expression. COC exposed to 100 ng/ml of GM-CSF during maturation did not display significant differences in terms of embryo cleavage rate (50.4% vs. 57.5%), blastocyst development at day 7 (31.9% vs. 28.7%) and at day 9 (17.4% vs. 17.9%) compared to untreated control (SOF alone, P = 0.2).
  
  
  CONCLUSIONS
  GM-CSF enhanced cumulus cell expansion of in vitro matured bovine COC. However, GM-CSF did not increase oocyte nuclear or cytoplasmic maturation rates, IGF-2 expression or subsequent embryonic development.
authors.forename: Oscar A
authors.initials: OA
authors.lastname: Peralta
authors.forename: Danai
authors.initials: D
authors.lastname: Bucher
authors.forename: Ana
authors.initials: A
authors.lastname: Fernandez
authors.forename: Marco
authors.initials: M
authors.lastname: Berland
authors.forename: Pablo
authors.initials: P
authors.lastname: Strobel
authors.forename: Alfredo
authors.initials: A
authors.lastname: Ramirez
authors.forename: Marcelo H
authors.initials: MH
authors.lastname: Ratto
authors.forename: Ilona
authors.initials: I
authors.lastname: Concha
mesh_terms: D000818:Animals; D002417:Cattle; D002452:Cell Count; D002467:Cell Nucleus / Q000187:drug effects; D054885:Cumulus Cells / Q000187:drug effects*; D003593:Cytoplasm / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D047108:Embryonic Development / Q000187:drug effects; D005260:Female; D005307:Fertilization in Vitro; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects; D066298:In Vitro Techniques; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis; D009865:Oocytes / Q000187:drug effects*
chemical_list: D007335:Insulin-Like Growth Factor II; D016178:Granulocyte-Macrophage Colony-Stimulating Factor